My 17-year old daughter bought a 99 Cherokee (4.0 - Automatic with 107K) this summer and it is running great except for occasionally it will just cut off while your going down the road. It will start right up everytime but this is not a good situation for my young driver to encounter. There is no engine code showing up on the computer but one clue that I'm hoping will solve it is that the speedometer will shoot up to 80-90 mph right before it cuts off even though you might be going 5 or 35 mph. I have changed out the plugs, wires, cap & rotor. I took it to a mechanic the other day and he drove it all day and could not recreate the problem. Any ideas or suggestions?

 

Mine was camshaft position sensor going bad, had some of same in cations - it findly quit and would not start.

 

one thing it could be is the cps located on the bellhousing,they get dirty and will quit working like you have described.
The other thing could be the camshaft position sensor.
I would start with these two and see if it helps.

 

tough one there... every reply has valid ideas but the 1 strange symptom is the speedo going up to 85-90 right before it stalls... sounds like a wiring problem somewhere or at least something electrical that will interfere with both the speedo and ignition... I haven't had a cps mess with a speedometer before but since it's all tied to the computer who knows... I would start by idling the vehicle and moving some wiring harnesses around to see if it will stall... other than that I would be curious to see what solves this one...

 

I called a mechanic yesterday and he called me back today. He felt pretty confident that the problem is with the speed sensor that is mounted to the transmission. He said that the part was about $50 and labor would be $70-80 to put it on. Any other ideas?

 

Really? $70-80 for labor on a speed sensor? Its not hard to find or get to, you can look under the jeep where the transfer case is and toward the back of the transfer case there should be some wires going into a plug on it...thats your speed sensor. Buy any sensors from Napa as I've had bad experiences with ones from Autozone and Advanced

 

Was driving me nuts because there was no rhyme or reason to when or why it would happen and it wouldn't stay dead to troubleshoot... It finally went belly up and a $50 ECU from the Bone-Yard has kept it running for almost 2 months now. (Knock, Knock…)

Not sure if my speedo issue went away but I know the Part time and ABS lights are gone now. I'll watch to see if my speedo still freaks out with the new ECU and let you know...

Not sure why the ECU would affect so many things, If I had my way, the only electronics I would have is the Alternator! On the up side, this is why the mechanic gave up and sold me the rig for $200.

 

The ECM controls darn near everything as far as making the Jeep run goes.

 

So is the speed sensor the same as the CPS, ECM and ECU? The mechanic said that you have to know how to install it or it will mess up. Any more directions on how to locate it and any tricks to take it off/install it?

 

No, the speed sensor actually measures the rotational speed of the transfer case output shaft. Its on the top of the transfer case towards the rear of the Jeep